Introduction

Q. Is DLSw+ supported on MSFC/MSFC2, and what feature set is required to run DLSw+ on MSFC/MSFC2 in the Catalyst 6500?

A. Yes, DLSw+ is supported on MSFC/MSFC2. The minimum feature set required for MSFC/MSFC2 is IP Plus. For MSFC, the image name should read c6msfc-is-mz.xxx, and for MSFC2, the image should read c6msfc2-is-mz.xxx, where xxx is the Cisco IOS® Software Release. It is highly recommended that you use the latest release that is available to registered users.

Q. What is the minimum Cisco IOS Software Release that supports DLSw+ on the MSFC, and what caveats of which should I be aware, when running DLSw+ on the MSFC/MSFC2 in general?

A. The minimum Cisco IOS Software Release that supports DLSw+ on the MSFC and MSFC2 is 12.1(1)E and 12.1(2)E, respectively. However, due to some well known caveats, listed in the next bullets, it is important that the latest Cisco IOS Software Release is used.

Note: For further information about these Cisco bug IDs, refer to the Bug Toolkit (registered customers only) and enter the specific bug ID.

CSCds55205—DLSw+ does not work with MSFC2. Integrated in 12.1(04.04)EC and 12.1(04.04)E.

CSCds70377—DLSw+ Ethernet Redundancy does not work on MSFC2. Integrated in 12.1(05.06)EC and 12.1(05.06)E.

Q. How does DLSw+ Ethernet Redundancy work, and for what is it intended?

A. The DLSw+ Ethernet Redundancy feature was introduced in Cisco IOS Software Release 12.0(5)T to provide redundancy and load balancing between multiple DLSw+ peers in an Ethernet environment. The feature also enables DLSw+ to support multiple DLSw+ routers on the same transparent bridged domain that can reach the same MAC address in a switched environment. DLSw+ Ethernet Redundancy was designed for the remote branch office side, not the central site hub-end. For more information on DLSw+ Ethernet Redundancy, refer to these documents:

Q. Is DLSw+ Ethernet Redundancy supported on the MSFC, and what kind of software do I need with it?

A. Yes, DLSw+ Ethernet Redundancy is supported on the MSFC. Refer to Question 2 for information about bugs of which you should be aware. The minimum feature IP Plus is also required. (Refer to Question 1.)

Q. Are there any disadvantages in running DLSw+ on the MSFC?

A. Yes. Because the Catalyst 6500 does not support Token Ring, and Ethernet does not support Routing Information Field (RIF), DLSw+ has no way to determine whether end-station device MAC addresses are sourced locally or remotely. This can result in problems with bridge loops, which can cause a Systems Network Architecture (SNA) session disruption. DLSw+ is also process intensive; to run any significant volume of DLSw traffic on the MSFC is counterproductive to the real purpose of a Layer 3 switch. For example, you have greater granularity in router CPU power and scalability with a 7200 Network Processing Engine/Network Service Engine (NPE/NSE) to handle the workload and failover redundancy requirements, than with the MSFC.

Note: You can run DLSw+ on an external router with an Inter-Switch Link (ISL) sub-interface instead of running DLSw+ on the MSFC.

Q. Are there any performance figures to enable me to compare MSFC against other platforms for DLSw+ with TCP?

A. Yes, there is a white paper on DLSw+ TCP Performance that shows the percentage of the CPU that is utilized on various Cisco Router platforms as a function of data frames transported between two DLSw+ TCP peers.

Q. Is DLSw+ Fast-Sequenced Transport (FST) encapsulation supported on the MSFC or MSFC2?

Q. Can I configure DLSw+ on two MSFC2 cards in the same chassis?

A. DLSw+ works on an MSFC; however, no official tests have been performed with two MSFC2s in the same chassis. DLSw+ code has no way to identify that the two MSFC2s are in the same chassis, and has no supporting code for anything like this. More importantly, DLSw+ Ethernet Redundancy is designed for the remote end, not for the central site. Ethernet Redundancy still assumes a Token Ring is on the central location.

Q. Where can I find a sample configuration for DLSw+ Ethernet Redundancy setup with an MSFC?

A. Consider this topology:

Note: MSFC2 and Router2 are DLSw+ Ethernet Redundancy peers.

Note: That topology was assembled in a lab environment with Ethernet media used for WAN connections. In reality, this is done with serial connections.

Note: Because all MAC addresses in the previous command are in non-canonical format, local MAC 4004.4004.4004 (0220.0220.0220) maps to the host MAC address 5555.5555.5555 and the backup 4088.4088.4088 (0211.0211.0211), which is the other redundant DLSw peer (Router2).

Note: The Client is configured to connect to 0201.0201.0201 in Router2 and not the host MAC address of 5555.5555.5555. (Alternatively, it can point to MSFC2 0220.0220.0220.) When Router2 recognizes the connection request to 0201.0201.0201 (which is 4080.4080.4080 after bitswap) Router2 maps this request to the host MAC address 5555.5555.5555. This is shown in this configured command on Router2: